Hadronic Transitions in Collisions above 4 GeV at BESIII Jianming Bian University of Minnesota

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1 + ee Hadronic Transitions in Collisions above 4 GeV at BESIII Jianming Bian University of Minnesota QWG2016, Pacific Northwest National Laboratory, Richland, WA, USA 1

2 Charmonium spectroscopy Below open-charm threshold, all states have been observed. Charm anti-charm potential models describe spectrum very well. Many missing states above open-charm threshold. 2

3 There are lots of XYZ states Y(4660) Y(4360) Y(4260) Y(4008) Z(4430) Z(4020) Z(3900) X(3872) A number of new states above open-charm threshold. Charmonium in the final state, but not an obvious charmonium state (charmoniumlike or XYZ) X: neutral, in B decays, Y transitions and hadron machines. Y: neutral, vectors in e + e - colliders. Z ± : charged quarkonium-like What are they? Charmonium? Tetraquark? Molecule? Hybrid? Hadrocharmonium? 3

4 BESIII data samples for XYZ study (5/fb) For the XYZ states study, BESIII has accumulated about 5 fb -1 data. Around ψ(4040), Y(4260), and Y(4360) peaks, we collected the largest data sample in the world so far for the study of their decays. Data samples with small statistics at other energy points are collected for the line-shape study. 4

5 Y-family states A family of vectors (J PC =1 -- ) observed in e + e - colliders. In the process e + e àγ ISR π + π J/ψ, the BaBar experiment observed the Y(4260), then confirmed by CLEO and Belle. Properties are different from charmonium: strong coupling to ππj/ψ, no significant enhancement in open charm production. At BESIII, vector ψ/y states can be produced directly. BaBar: [PRL95, ],273fb-1 Y(4260)àπ + π - J/ψ Belle [PRL 99, (2007)] 673fb -1 Y(4360), Y(4660) àπ + π - ψ(2s) 5

6 Observation of e + e - π + π - h c (1P) Born cross section (pb) Belle: π + π J/ψ BESIII: π + π - h c CLEO-c: π + π - h c Belle: PRL110, (2013) BESIII: PRL111, (2013) CLEO-c PRL107, (2011) E CM (GeV) 4.26 GeV 4.36 GeV h c (1P)àγη c h c (1P)àγη c J/ψ(1S) cc h c (1P) cc Reconstruct h c γη c, η c hadrons [16 exclusive decay modes] σ(e + e - π + π - h c ) ~ σ(e + e - π + π - J/ψ) but line shape different Local maximum ~ 4.23 GeV for e + e - π + π - h c Broad structure at high energy region? 6

7 BESIII [PRL (2013)] Z c (3900) ± and Z c (4020) ± in e + e - π + π - h c (1P),π + π - J/ψ BESIII[PRL (2013)] 525pb 4.26GeV e + e - àπ + π - h c e + e - àπ + π - J/ψ Narrow π ± h c structure observed *M = ±0.8±2.7 MeV *Γ= 7.9±2.7±2.6 MeV *Significance : 8.9σ Hint for Z c (3900)àπ ± h c? *Significance is only 2.1σ J/ψ(1S) cc h c (1P) cc Both ππj/ψ and ππh c have large non-z c components. Z c (3900) mainly decays to πj/ψ and Z c (4020) mainly decays to πh c 7

8 Z b (10610) ± and Z b (10650) ± Belle [PRL108, (2012)] fb -1 e + e - àυ(5s)àπ + π - Υ(nS) e + e - àυ(5s)àπ + π - h b (mp) Z b (10610)àπΥ(2S) Z b (10650)àπΥ(2S) Z b (10610)àπh b (1P) Z b (10650)àπh b (1P) Z b (10610) Z b (10650) Heavy flavor partners of Z c? But: ππυ have large non-z b components ππh b have small non-z b components 8

9 XYZ+R-Scan Data for π + π - h c cross-section lineshape measurement at BESIII Data samples: XYZ sample: 17 energy points from 3896 MeV to MeV total luminosity: 5.26 fb -1 R-scan data sample: 62 energy points from 4097 MeV to 4587 MeV total luminosity: 0.51 fb -1 Decay channel: e + e - π + π - h c, h c γη c, η c X i X i ={pp-bar, π + π - K + K -, π + π - pp-bar, 2(K + K - ), 2(π + π - ), 3(π + π - ), 2(π + π - )K + K -, K S0 K + π - +c.c., K S0 K + π - π + π - +c.c., K + K - π 0, pp-barπ 0, K + K - η, π + π - η, π + π - π 0 π 0, 2(π + π - )η, 2(π + π - π 0 ) } ) -1 Luminosity (pb R-scan data sample XYZ data sample s (GeV) 9

10 Fit to the π + π - h c cross section!!! =!!!!! +!!"!!!!!!!!!!!! B i (m): constant width Breit-Wigner funcbon P(m): 3-body phase space factor φ: relabve phase between two resonances significance of two structures assumpbon over one structure > 10 σ! Dressed Cross section (pb) 250 BESIII: R-scan data sample BESIII: XYZ data sample Fit curve: Total Fit curve: Y(4220) Fit curve: Y(4390) s (GeV) M (MeV) Γ tot (MeV) Γ eebr (ev) φ (rad) Y(4220) ±4.0± ±9.0± ±4.1± Y(4390) ±6.3± ±16.1± ±9.7± ±1.5±0.2 10

11 Fit to the π + π - h c cross section 200 summary Width (MeV) Y(4220) stucture in ωχ c0 Y(4260) Y(4360) Y(4390) ψ(4415) Cross section of e + e - π + π - h c has been measured at 79 energy points from 3896 MeV to 4600 MeV The cross section drops in high energy region, likely two resonant structures The significance of the two resonant structures assumption over one structure is larger than 10σ Mass (MeV) Parameters of the two resonances are different from those of Y(4260), Y(4360), and the ψ(4415) 11

12 e + e - àωχ c0 are observed at 4230 MeV and 4260 MeV. Signal does not arise from the decays of the Y(4260). Fit with a single BW Mass = 4230±8±6 MeV Width = 38±12±2 MeV Significance > 9σ Observation of e + e - à ωχ c GeV 4.23 GeV 4.23 GeV 4.36 GeV A tetraquark? [PRD 91, (2015)] ψ(4s)? [EPJC 74, 3208 (2014)] Threshold effect? ωχ c0 Phys. Rev. Lett. 114, (2015) 12

13 Observation of e + e - à η(η )J/ψ Agree with previous results with improved precision Structure around 4.2 GeV ψ(4160)àηj/ψ Cannot tell the line shape due to statistics Cross-section is much lower than ηj/ψ 13

14 No Y(4260)à ηπ 0 J/ψ n Model predictions of e + e - à ηπ 0 J/ψ n Hadro-quarkonium/tetraquark of Z b and Z c : p M.Voloshin, PRD p A. Ali et al., PRL , PRL p L. Maiani et al., PRD n Y(4260) as a D 1 D molecule: X. Wu et al., PRD 89, PRD92, (2015) Ø Upper limits well above prediction of D 1 D molecule model (0.05 pb at GeV) [X. G. Wu et al., PRD 89, ] Ø Need ~100 times more luminosity to reach the sensitivity 14

15 What are the Y states? Between 4 and 4.7 GeV, at most 5 states expected (3S, 2D, 4S, 3D, 5S), 7 observed Hybrids are expected in this mass region Molecular states? Cannot rule out threshold effect/fsi/ The Ys are all narrow and similar π + π - h c, ωχ c, have add complexity but also give hints for their composition 15

16 Thank you! 16

17 Backup 17

18 BEPC II: a double-ring machine 8ns 2.5m RF 22 mrad RF Compton back-scattering for high precision beam energy measurement BESIII is here 0.1cm 1.5cm Beam energy: GeV Luminosity: cm -2 s -1 Optimum energy: 1.89 GeV Energy spread: No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A SR mode: 2.5 GeV IP 18

19 BESIII data samples Note that luminosity is lower at J/ψ, and machine is optimal near ψ peak Integrated lum.: Jan June 2014 about 9 fb different energies Note increase in slopes! ψ : 2.9 fb -1 ψʹ: 0.5 B J/ψ: 1.3 B XYZ: 5.0 fb -1 [ ] 2011: ψ & ψ(4040) 2012: ψʹ & J/ψ [0.35B & 1.0B] 2010: ψ 2009: ψʹ & J/ψ 19

20 List of Y-family states State Mass (MeV/c 2 ) Width (MeV/c 2 ) Decay mode Experiment Y(4008) ±97 π + π - J/ψ Belle Y(4260) 4250±9 108±12 π + π - J/ψ π 0 π 0 J/ψ K + K - J/ψ BaBar CLEO Belle Y(4360) 4361±13 74±18 π + π - ψ(2s) Belle BaBar Y(4630) Λ c+ Λ c - Belle Y(4660) 4664±12 48±15 π + π - ψ(2s) Belle BaBar 20

21 e + e - π + π - h c (1P) at BESIII h c γη c, η c hadrons [16 exclusive decay modes] pp, π + π - K + K -, π + π - pp, 2(K + K - ), 2(π + π - ), 3(π + π - ) 2(π + π - )K + K -, K S0 K + π - +c.c., K S0 K + π - π + π - +c.c., K + K - π 0 ppπ 0, K + K - η, π + π - η, π + π - π 0 π 0, 2(π + π - )η, 2(π + π - π 0 ) E cm =4.26 GeV E cm =4.36 GeV BESIII: arxiv: , PRL111,

22 Observation of e + e - π + π - h c (1P) E cm =4.26 GeV E cm =4.36 GeV N(h c )=416±28 Lum=827/pb σ B = 41.0±2.8±7.4 pb N(h c )=357±25 Lum=544/pb σ B = 52.3±3.7±9.2 pb BESIII: arxiv: , PRL111,

23 Fit to the π + π - h c cross section: signal at 4415 MeV ) 2 (GeV/c M η c ) 2 Events / ( GeV/c M γη (GeV/c ) c M γη (GeV/c ) c Number of signal events extracted from π + π - recoil mass spectrum: XYZ sample: fit to the mass spectrum R-scan sample: calculate by counbng the entries in h c signal region and the entries in h c sideband regions 23

24 Fit to the π + π - h c cross section!!"#$$#! =!!"# L 1 +!!"!!! B(!!!! )B(h!!!! )!!! Dressed Cross section (pb) BESIII: R-scan data sample BESIII: XYZ data sample CLEO: 4170 data sample stabsbcal uncertainty only s (GeV) 24

25 Fit to the π + π - h c cross section: Cross secbon measurement Total: 15.2%-18.0% depending on CM energies Luminosity: 1% Branching fracbon of h c γη c :11.8% DetecBon efficiency and branching fracbon of η c : 6.4%-9.1% efficiency: 5.5%-10.8%, depend on the η c decay modes and CM energies Systematic uncertainty ISR correcbon factor: 0.1%-2.0% Number of signal events extracbon: 2.0%-10.0% 25

26 Fit to the π + π - h c cross section: Systematic uncertainty Parameters of the structures CM energy 1 : systemabc uncertainty of center-of-mass energy measurement CM energy 2 : assumpbons made in the center-of-mass energy measurement for R- scan data sample Cross secbon 1 : systemabc uncertainbes of the cross secbon measurement which are different in each energy point Cross secbon 2 : systemabc uncertainbes of the cross secbon measurement which are common in each energy point 26

27 Observation of e + e - à η J/ψ BESIII Preliminary 4.23 GeV BESIII Preliminary 4.26 GeV NEW! 27

28 Observation of e + e - π + π - h c (1P) σ(e + e - π + π - h c ) ~ σ(e + e - π + π - J/ψ) but line shape different Local maximum ~ 4.23 GeV Non-Zc ππh c take a large proportion 28

29 No significant e + e - à γy(4140) 4.23 GeV 4.26 GeV NEW! 4.36 GeV Sum of all data sets BESIII: arxiv: , PRD (in press) 29

30 Observation of e + e - à ηj/ψ BESIII preliminary 4.23 GeV BESIII preliminary 4.26 GeV BESIII preliminary 4.23 GeV BESIII preliminary 4.26 GeV 30

31 No significant e + e - à ηπ 0 J/ψ n Model predictions of e + e - à ηπ 0 J/ψ n Hadro-quarkonium/tetraquark of Z b and Z c : p M.Voloshin, PRD p A. Ali et al., PRL , PRL p L. Maiani et al., PRD n Y(4260) as a D 1 D molecule: X. Wu et al., PRD 89, n Select an η and a π 0, then check the J/ψ signal NEW! s = GeV s = GeV BESIII preliminary 31

32 Hadrons:normal & exotic In the quark model, hadrons are dominantly bound states of qqbar (mesons) or qqq (baryons) But QCD allows hadrons with N quarks 2, 3 Glueball:N quarks =0 (gg, ggg, ) Hybrid: N quarks = 2 + excited gluon Multiquark state: N quarks > 3 Molecule: bound state of 2 or more hadrons It is a long history of searches for these exotic hadrons, however, no solid experimental evidence was found until recent breakthroughs in the charmonium region. 32

33 Beijing Electron Positron Collider II (BEPCII) Linac: The injector, a 202m long electron position linear accelerator that can accelerate the electrons and positrons to 1.3 GeV. BESIII: Beijing Spectrometer III, generalpurpose detector for BEPCII. Beam energy: GeV Luminosity: cm-2s-1 The storage ring: A sports track shaped accelerator with a circumference of 237.5m. 33

34 The BESIII Detector Magnet yoke SC magnet, 1T RPC Muon Counter TOF, 90ps Be beam pipe MDC, 120 µm A total weight of 730t, ~40,000 readout channels, data rate 6,000Hz ~50Mb/s CsI(Tl) calorimeter, 2.5 %@ 1 GeV 34

35 BESIII Collaboration US (5) Univ. of Hawaii Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana Europe (13) ~400 members 53 institutions from 11 countries Germany: Univ. of Bochum, Univ. of Giessen, GSI Univ. of Johannes Gutenberg Helmholtz Ins. In Mainz Russia: JINR Dubna; BINP Novosibirsk Italy: Univ. of Torino, Univ. of Ferrara, Frascati Lab Netherland:KVI/Univ. of Groningen Sweden: Uppsala Univ. Turkey: Turkey Accelerator Center Pakistan (2) China(31) Univ. of Punjab IHEP, CCAST, GUCAS, Shandong Univ., Univ. of Sci. and Tech. of China COMSAT CIIT Zhejiang Univ., Huangshan Coll. Huazhong Normal Univ., Wuhan Univ. Zhengzhou Univ., Henan Normal Univ. Peking Univ., Tsinghua Univ., Zhongshan Univ.,Nankai Univ. Shanxi Univ., Sichuan Univ., Univ. of South China Hunan Univ., Liaoning Univ. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Suzhou Univ., Hangzhou Normal Univ. Lanzhou Univ., Henan Sci. and Tech. Univ. Beihang Univ., Beijing Petrol Chemical Univ. Korea (1) Seoul Nat. Univ. Japan (1) Tokyo Univ. 35

36 E cm BESIII/BEPCII GeV BESIII (Preliminary) Physics programs at BESIII include light-hadron and charmonium spectroscopy, electroweak and strong physics at the charm scale, tauphysics, R value measurement and searches for rare processes. 36

37 Data collected over time 37